The Twelfth Argument:

These essential attributes may be known without thereby yielding a conception of the innermost nature of the thing defined, as in this example and others. It is thus clear that knowing them does not guarantee an understanding of the essence.

The Thirteenth Argument:

If a definition has two components, both must be conceived, as with “living being” and “rational.” If each component requires a definition, this entails an infinite regress or circularity. If, however, the components are conceived in themselves without a definition—whether the conception is of a living being, a sentient being, something that moves voluntarily, something that grows, or a body—then it is well known that these are more general.

If they are more general because the senses perceive a greater number of their instances, then, if sensory perception of their instances suffices to form a conception, the senses have also perceived instances of the species. If it does not suffice, however, the components are not known. Thus, the thing to be defined requires something to define it, and the components of the definition require a definition.